A neural network for a control unit is described in German Patent Application No. DE 10 2005 050 577 A1. The neural network 1 for a control unit is tested. The neural network has a plurality of first neurons N1, N2, . . . , Nn in a first layer, and a second neuron M in a second layer following the first layer. Each test-signal combination is selected from a predefined plurality of test-signal combinations. Each test-signal combination assigns a test-input-signal vector ut1, ut2, . . . , utk to each first neuron N1, N2, . . . , Nn, which is either a zero signal or saturates the associated first neuron N1, N2, . . . , Nn in such a way that the first neuron N1, N2, . . . , Nn outputs a lower saturation value cpmin, or saturates associated first neuron N1, N2, . . . , Nn in such a way that first neuron N1, N2, . . . Nn outputs an upper saturation value. The test-signal combination is applied to first neurons N1, N2, . . . , Nn, and output signal p of second neuron M is acquired. A partial test signal is stored when output signal p is greater than a predefined threshold value. A positive total test signal is output after each of the test-signal combinations has been applied and when no partial test signal is stored for the predefined plurality of test-signal combinations.